class_docstr: Sub-lexer for raw E-mail. This lexer only process header part of e-mail.
  
  .. versionadded:: 2.5
code: def get_x_header_tokens(self, match):
      if self.highlight_x:
          # field
          yield match.start(1), Name.Tag, match.group(1)
  
          # content
          default_actions = self.get_tokens_unprocessed(
              match.group(2), stack=("root", "header")
          )
          for item in default_actions:
              yield item
      else:
          # lowlight
          yield match.start(1), Comment.Special, match.group(1)
          yield match.start(2), Comment.Multiline, match.group(2)
  
file_path: catboost/contrib/python/Pygments/py2/pygments/lexers/email.py
imports: from pygments.lexer import RegexLexer, DelegatingLexer, bygroups
  from pygments.lexers.mime import MIMELexer
  from pygments.token import Text, Keyword, Name, String, Number, Comment
  from pygments.util import get_bool_opt
label_desc: Use image node_id 2 for calling the EmailHeaderLexer obj's underlying member method code with example usage: obj.get_x_header_tokens(match) without return types